I was close to crashing some time ago, it was raining and my runflats were utter crap.. After breaking hard the ABS came in and i slid across the road for about 8 meters. Then came to a stop, i remember seeing the hazards come on as soon as i lost traction on the 4 wheels, i had to press the hazard button to turn them off when i recovered from the shock.

In any case, the car will warn the ones behind you when you get into trouble.